Fighting to shake off his party-boy image since the success of “The Social Network,” Facebook billionaire Sean Parker insists rumors of his past drug use mean he’s been “stigmatized by a victimless crime.”

The charismatic Facebook founding president, worth about $1.6 billion, is depicted in the hit movie as a hard-partying nerd by Justin Timberlake, whose character parties with others using cocaine.

Parker’s parties at his $20 million Greenwich Village townhouse named, after Bacchus, the Roman god of intoxication, and a 2005 drug-related arrest (which didn’t result in charges) seem to reinforce that image.

He told us, “There’s a certain pressure from the press and even from the people I meet to live up to that reputation that’s been created by the film.”

Parker hosted a celeb-packed after-party at the Coachella festival in April that lasted until after 4 a.m. “Even if I set out to throw a really small party, there’s expectations about what it’s going to be like. People assume it’s going to be a wild, crazy thing,” he said.

He refused to say whether he currently uses drugs but said, “It is an individual decision that doesn’t hurt others, and it’s a victimless crime as long as you’re not hurting yourself. You end up with collateral [reputation] damage because it is stigmatized.”

Of “The Social Network,” Parker said, “I take less of an issue with the depiction of drug use than I do with . . . [the depiction of my] behavior to other people.”

A “pro-individual liberty” activist, Parker last year donated $100,000 to back California’s proposition 19 to legalize marijuana. “It’s inconvenient for me to take a stand on this issue,” he told us. “I’m certainly not making anything easier on myself [professionally].”

Parker is an investor in music service Spotify and recently made an unsuccessful bid to buy a stake in Warner Music with Ron Burkle. Parker and girlfriend Alexandra Lenas were engaged in April. They have yet to set a wedding date. He joked, “If I talk about it without her here, she will kill me.”